A digital signal cross-connect panel is typically used by a telephone central office to passively cross-connect digital telecommunication equipment, such as a fiber multiplex having fiber multiplexer (MUX) circuits and a digital loop carrier having digital loop carrier circuitry. Such panels are typically known as digital signal cross-connect panels (or DSX panels), and provide a means for terminating the input and output circuits of digital telecommunication equipment to be interconnected. A conventional DSX panel has a portion for terminating the input and output circuits of the digital equipment to be interconnected, a portion for selective cross-connection of the input and output circuits of the digital equipment and a test access jack for each of the input circuits and for each of the output circuits of the digital equipment. The digital telecommunication equipment with which a DSX panel is currently used operates at the DS1 line rate of 1.544 mbs (T1/T1C line rates). DSX panels are usually configured to terminate the number of circuits matching the number of circuits used by the digital equipment to be interconnected. For example, if a single DSX panel is to be used with a typical digital fiber multiplexer having 28 multiplexer (MUX) circuits to be cross-connected to a typical digital loop carrier having 28 digital loop carrier (DS1) circuits, the DSX panel would require 56 available termination ports. The DSX panel would have 28 multiplexer termination ports to which the 28 multiplexer circuits would be connected and 28 carrier ports to which the 28 digital loop carrier circuits would be connected. Alternatively, 28 termination ports could be provided by one DSX panel and 28 termination ports by a second DSX panel if two panels were used. It is noted that each of the multiplexer circuits and each of the digital loop carrier circuits includes an input tip and ring circuit and an output tip and ring circuit, and thus each has four wires which must be terminated on the DSX panel. The DSX panel multiplexer and carrier termination ports each typically comprise four terminals, such as four wire wrap posts about which the four wires of a multiplexer or digital loop carrier circuit are wrapped.
The cross-connect portion of the DSX panel provides a means to make desired semi-permanent cross-connections between the multiplexer circuits and the digital loop carrier circuits of the digital equipment to be interconnected by the panel. For the example DSX panel referred to above, the cross-connect portion would have 28 multiplexer cross-connect ports and 28 carrier cross-connect ports, each having four terminals, such as four wire wrap posts. In conventional fashion, a selected one of the multiplexer circuits is interconnected to a selected one of the digital loop carrier circuits by hard-wiring together the corresponding multiplexer cross-connect port and the corresponding carrier cross-connect port. This is accomplished by making a hard-wire connection between an output tip terminal of the multiplexer cross-connect port and an input tip terminal of carrier cross-connect port, making a hard-wire connection between an output ring terminal of the multiplexer cross-connect port and an input ring terminal of the carrier cross-connect port, making a hard-wire connection between an output tip terminal of the carrier cross-connect port and an input tip terminal of the multiplexer cross-connect port, and making a hard-wire connection between an output ring terminal of the carrier cross-connect port and an input ring terminal of the multiplexer cross-connect port.
The multiplexer cross-connect ports and the corresponding multiplexer termination ports are electrically connected together internal of the DSX panel, and the carrier cross-connect ports and the corresponding carrier termination ports provided are electrically connected together internal of the DSX panel. These connections usually incorporate test access jacks, as will be described below.
After digital equipment is interconnected using a DSX panel, it is sometimes necessary to access and test the circuits of the multiplexer and digital loop carrier equipment. To do this, a conventional DSX panel has a set of test access jacks for each multiplexer termination port and a set of test access jacks for each carrier termination port. In other words, a DSX panel which interconnects 28 multiplexer circuits with 28 digital loop carrier circuits has a total of 56 sets of test access jacks. A set of test access jacks for a particular multiplexer or carrier termination port permits serial and bridged access to the input and output multiplexer or digital loop carrier circuits connected to the termination port.
Typically, a set of test access jacks comprises three Bantam jacks identified as an output jack, an input jack and a monitor jack. The output and input jacks each have a tip contact and a ring contact, and each of the tip and ring contacts has a spring arm contact which is in electrical contact therewith when no test plug is plugged into the jack and out of electrical contact therewith when a test plug is plugged into the jack. The electrical connections between the multiplexer and carrier termination ports and the corresponding multiplexer and carrier cross-connect ports are usually made through the output and input jacks for the termination ports.
In particular, the terminals of each multiplexer and carrier termination port are connected to the corresponding tip and ring contacts of the output and input jacks of the set of test access jacks for the termination port. The spring arm contacts for these tip and ring contacts are connected to the corresponding terminals of the corresponding multiplexer or carrier cross-connect port. In such fashion, when no test plug is inserted into the output or input jacks, a direct electrical path exists between the terminals of the termination port and the corresponding multiplexer or carrier cross-connect port. If a test plug is inserted into the output and input jacks for the termination port, the insertion causes both the spring arm contacts of each jack to break electrical contact with their corresponding tip and ring contacts and to disconnect the corresponding output and input terminals of the termination port from the corresponding output and input terminals of the corresponding multiplexer or carrier cross-connect port. Of course, this also connects the tip and ring contacts of the inserted test plugs through the tip and ring contacts of the output and input jacks to the corresponding termination port. Thus, the test plug provides serial access to the multiplexer or digital loop carrier circuit connected to the termination port for testing of the circuit or for temporary patching of the circuit to another circuit terminated on the DSX panel (other than the one connected on a semi-permanent basis through the existing hard-wire connection provided by the multiplexer and carrier cross-connect ports).
For example, when a patch cord is used with a test plug which is inserted into the output jack for a multiplexer termination port to which a multiplexer circuit is connected, the plug on the other end of the patch cord can be inserted into the input jack for a selected carrier termination port to which a digital loop carrier circuit is connected, other than the carrier termination port to which the multiplexer termination port is already connected through the hard-wiring of the corresponding cross-connect ports. This allows a user of the DSX panel to temporarily make a new connection between the multiplexer circuit and a different digital loop carrier circuit, and also temporarily bypass the digital loop carrier circuit to which connected through the cross-connect ports. Of course, to make a complete patch between digital equipment multiplexer and digital loop carrier circuits, two patch cords must be used, one to connect the output tip and ring circuit of the multiplexer circuit to the input tip and ring circuit of the digital loop carrier circuit, and the other to connect the input tip and ring circuit of the multiplexer circuit to the output tip and ring circuit of the digital loop carrier circuit.
In such manner, the first circuit of a multiplexer which is connected via the semi-permanent cross-connection provided by the cross-connect ports of the DSX panel to the first circuit of a digital loop carrier, can be temporarily disconnected from the first digital loop carrier circuit and connected to any one of the other digital loop carrier circuits using two patch cords. In like fashion, the first digital loop carrier circuit can be temporarily disconnected from the first multiplexer circuit and connected to any one of the other multiplexer circuits using two patch cords. This is useful when testing to determine if circuits are working correctly, and when making temporary connections while circuits are being repaired.
The third test access jack is the monitor jack. The monitor jack has its tip and ring contacts connected through resistors to the spring arm contacts of the output jack for the termination port. This provides a bridge access which is used to monitor for pulses or errors or patching or rolling in the multiplexer and digital loop carrier circuits which are connected together by the DSX panel. The monitor jack is connected so as to not disturb the circuits. Typically, resistor values are chosen which provide at least 20 dB of isolation from the working circuits.
While the prior art DSX panel just described functions well, it is desirable to reduce the cost of the panel and to also increase the circuit handling capacity of the panel. For a DSX panel that is six inches high and four inches in depth and designed to mount in an industry standard 23-inch equipment rack or cabinet with a WECo one-inch mounting hole, current DSX panels provide a maximum of about 64 termination ports. When using a single DSX panel, the panel can accommodate a telephone system which has a maximum of 32 multiplexer circuits and 32 digital loop carrier circuits. If the telephone system has more circuits, it is necessary to use two or more DSX panels, and hence take up greater space in the equipment rack where the DSX panels are mounted. It would be desirable to increase the current 64-port maximum density to at least 168 ports so that the DSX panel can interconnect as many as 84 multiplexer circuits and 84 digital loop carrier circuits. While it is desirable to increase the number of digital equipment circuits that can be handled by the DSX panel, it is necessary that the panel still have the ability to access and test each of the circuits connected to each termination port. The present invention fulfills these needs, and further provides other related advantages.